1. Field of the Invention
The present invention relates to an etchant for metal alloy and an etching method using the etchant, and particularly to an etchant used for etching metal alloy having hafnium and molybdenum.
2. Description of Related Art
As the level of integration of integrated circuits increases, the dimensions of semiconductor devices decrease correspondingly. Since contact resistance is in opposite proportion to contact area, when the dimensions of transistors in metal oxide semiconductors (MOS) keep shrinking and the dimensions of a device also decrease, the contact resistance thereof increases accordingly such that the driving capability of the device is affected. Nowadays, refractory metals, refractory metal nitride and refractory metal oxide have been used in many researches and studies to replace conventional transistor materials to serve as conductive layers, dielectric layers and barrier layers.
Molybdenum and hafnium have characteristics of suitable work functions, low resistance and high thermal stability, and are therefore extensively applied in the semiconductor process. In recent years, it is found that metal alloy material having hafnium and molybdenum can be applied in fabricating N-type channel metal oxide semiconductor (MOS) transistors and P-type channel metal oxide semiconductor (MOS) transistors. However, no suitable etchant has been found so far that can etch metal alloy having hafnium and molybdenum, which has thus limited development of metal alloy having hafnium and molybdenum.